With the increasing reduction in weight, thickness, and size of 3C electronic products, there is an increasing demand for portable energy sources. Defects of conventional colloidal or solid electrolyte thin film batteries, for example, a lithium-ion battery, are that capacitance cannot be improved due to low energy density when current density is high, and charging and discharging are also unstable when current density is high.
Please refer to U.S. Pat. No. 7,540,886 B2 entitled “METHOD OF MANUFACTURING LITHIUM BATTERY”. The patent provides a method of manufacturing an all-solid lithium battery. A lithium battery manufactured by using this method is a lithium battery with a layered structure. Because a contact area between a solid active material and a solid electrolyte is insufficient, a part exceeding a thickness of 400 nm of a film of a lithium cobalt oxide (LiCoO2) all-solid thin film battery cannot be fully utilized during charging and discharging when current density is high.
Please refer to Taiwan Patent No. TW200919802 entitled “SOLID-STATE BATTERY AND METHOD FOR MANUFACTURING OF SUCH A SOLID-STATE BATTERY”. The patent provides a method for manufacturing a solid battery. However, the battery is a layered stack solid battery, and capacitance of the battery per unit area cannot be improved effectively when current density is high.
Please refer to European Patent No. EP1928051 entitled “THIN FILM LITHIUM BATTERY”. The patent provides a patterned electrode material. A battery in the patent is a dislocation solid battery with a layered structure, and an objective is to prevent occurrence of a pinhole effect which results in a short circuit in the lithium-ion thin film battery. Therefore, capacitance of the battery per unit area cannot be improved effectively when current density is high.
Please refer to Japanese Patent No. JP2013080669 entitled “LITHIUM-ION BATTERY”. The patent provides a 450 nm silicon thin film as an anode. A battery in the patent has great capacitance, but it is also a solid battery with a layered structure, and therefore capacitance of the battery per unit area still cannot be improved effectively when current density is high.
In view of the foregoing technical background, the present invention provides a thin film battery structure and a manufacturing method thereof. During charging and discharging when current density is high, a battery in the present invention has great capacitance and a long cycle life, and utilization of an electrode including an active material is improved, thereby reducing manufacturing costs of capacitance per unit.